One is just a massive single eruption, which would kill us all, the other is a thousand-year flood basalt eruption, which would also kill us.

The problem is that two enormous "thermochemical piles" of molten rock about 3,000 miles across are moving towards each other at the bottom of the Earth's mantle.

The piles have been known about for decades, but it was originally thought they were static.

But after extensive study with seismic waves, Thorne is convinced they're in fact moving together. The result is a massive, molten blob that will one day be created beneath the ocean, creating a huge amount of pressure that will eventually blow up in our face.

"What we may be detecting is the start of one of these large eruptive events that – if it ever happens – could cause very massive destruction on Earth," said Thorne.

Luckily the process is slow - it shouldn't happen for another 100 million years or so.